Active energy ray-curable inkjet ink, inkjet recorded article, and method for producing inkjet recorded article

ABSTRACT

An active energy ray-curable inkjet ink containing polymerizable compounds and a polymerization initiator, wherein the polymerizable compounds include at least 5 types of polyfunctional polymerizable compounds having molecular weights within a range from 150 to 500, and include substantially no monofunctional polymerizable compounds.

TECHNICAL FIELD

The present invention relates to an active energy ray-curable inkjetink, an inkjet recorded article using the same, and a method forproducing an inkjet recorded article.

BACKGROUND ART

Inkjet printing is a printing method in which very fine liquid dropletsof an ink composition are jetted from an inkjet head onto a printingsubstrate to print images or text or the like, and has thecharacteristic feature of not requiring a printing plate. Compared withconventional offset printing or gravure printing, the inkjet printingmethod is superior in terms of the initial cost of the apparatus, therunning costs during printing, and the apparatus size, but has tended tobe inferior in terms of image quality. Accordingly, inkjet printing nowmainly employs multi-pass printing in which the image quality isimproved by moving the inkjet head multiple times (at least two times)back and forth across the sub-scanning direction while the recordingmedium is transported in the main scanning direction, but because theproductivity is poor, the method is only used for printing small lots ofvarious different articles.

In recent years, as the density (resolution) of inkjet heads hasincreased and the image quality has improved as a result of factors suchas smaller liquid droplets, single-pass printing, in which printing isperformed in a single pass onto a transported recording medium while theinkjet head is held in a fixed position, and which is capable oflarge-lot high-speed printing, is expected to provide an alternative tooffset printing and gravure printing. Accordingly, various types ofinkjet inks including solvent inkjet inks, aqueous inkjet inks andenergy ray-curable inkjet inks are under investigation.

Among these types of inks, active energy ray-curable inkjet inks aresuperior to aqueous inkjet inks in terms of fast drying properties,coating film durability, and adhesion to a variety of recording media.As a result, there is much expectation for the use of such active energyray-curable inks in food packaging, which requires a high level ofproductivity and employs a large variety of recording media.

However, compared with active energy ray-curable offset inks which areconventionally used in food packaging applications, because activeenergy ray-curable inkjet inks are jetted as very fine ink droplets froman inkjet head having very fine nozzles, the inks must be designed witha low ink viscosity, and therefore low-molecular weight andlow-viscosity polymerizable compounds and low-molecular weightpolymerization initiators are used. As a result, a problems arises inthat unreacted polymerizable compound and unreacted polymerizationinitiator within the cured film is prone to movement (hereafter referredto as “migration”) into the packaged food. Consequently, these inkjetinks tend not to satisfy regulations relating to the level of migrationof substances from the ink coating film through the packaging material(for example, the Swiss Ordinance), which have been provided from theviewpoint of food safety.

Accordingly, in an attempt to suppress migration, for example, PatentDocument 1 discloses a curable liquid for food packaging applicationswhich either contains no initiator or contains a polyfunctionalinitiator, a large-molecular weight initiator or a polymerizableinitiator, and uses a polymerizable compound having an acrylate groupand a second ethylenic unsaturated polymerizable functional group, andan acrylate having a large number of functional groups.

Further, Patent Document 2 discloses an active light ray-curable inkjetink resistant to migration which uses a specific photoinitiator and inwhich the photopolymerizable compound uses only polyfunctionalphotopolymerizable compounds.

Further, Patent Document 3 discloses an active energy ray-curable inkjetink composition which uses 30 to 65% by weight of2-(2-vinyloxyethoxy)ethyl acrylate and 30 to 65% by weight ofdipropylene glycol diacrylate, and leaves only small amounts of residualcomponents within the cured film.

Furthermore, Patent Document 4 discloses a recording method forobtaining a cured film ideal for food packaging, the method involvingcuring, under low-oxygen concentration conditions, an active energyray-curable inkjet ink in which the weight ratio of the amount ofinitiator relative to the amount of monomer is within a range from 0.02to 0.16.

However, with the curable liquid of Patent Document 1 and the activelight-curable inkjet ink of Patent Document 2, although some suppressionof migration is possible, the suppression is still inadequate, andbecause a high-molecular weight initiator is used, another problemarises in that the high-speed jetting properties from the inkjet headtend to deteriorate, making high-speed printing impossible.

Furthermore, polymerizable compounds having a large number of functionalgroups tend to cause shrinkage of the coating film during curing,increasing the hardness of the cured coating film, and therefore thesecompounds are unsuitable for food packaging which uses comparativelythin plastic films (film thickness: 10 to 25 μm) and requiresflexibility. Moreover, many polymerizable compounds having a largenumber of functional groups have a high viscosity, meaning the jettingproperties at high speed tend to deteriorate. Further, with the activelight-curable inkjet ink of Patent Document 3, although the jettingproperties are favorable, migration suppression remains a problem.Furthermore, in the method for producing a cured film of an activelight-curable inkjet ink described in Patent Document 4, although somesuppression of migration is possible by reducing any polymerizationinhibition caused by oxygen, the level of suppression is still notadequate.

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: JP 2011-502188 A

Patent Document 2: JP 2017-105902 A

Patent Document 3: JP 2014-70135 A

Patent Document 4: JP 2015-80921 A

SUMMARY OF INVENTION Problems Invention Aims to Solve

Embodiments of the present invention have been developed in light of theabove circumstances, and relate to an active energy ray-curable inkjetink that exhibits excellent jetting properties at high speed, isresistant to migration and has a cured coating film (with goodflexibility and low shrinkage) that is suitable for food packaging, aswell as an inkjet recorded article that uses this active energyray-curable inkjet ink, and a method for producing an inkjet recordedarticle.

Means for Solution of the Problems

As a result of intensive investigation aimed at resolving the issuesdescribed above, the inventors of the present invention discovered thatan active energy ray-curable inkjet ink described below and a recordingmethod using that ink were able to address the above issues, thusenabling them to complete the present invention.

In other words, one embodiment of the present invention relates to anactive energy ray-curable inkjet ink containing polymerizable compoundsand a polymerization initiator, wherein

the polymerizable compounds include at least 5 types of polyfunctionalpolymerizable compounds having molecular weights within a range from 150to 500, and

include substantially no monofunctional polymerizable compounds.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein the atleast 5 types of polyfunctional polymerizable compounds having molecularweights within a range from 150 to 500 are composed of at least one typeof compound selected from the group consisting of difunctionalpolymerizable compounds and trifunctional polymerizable compounds.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein the atleast 5 types of polyfunctional polymerizable compounds having molecularweights within a range from 150 to 500 are difunctional polymerizablecompounds, and

the amount of each of the difunctional polymerizable compounds is,independently, from 5 to 50% by mass relative to the total mass of theink.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein one of thepolyfunctional polymerizable compounds having molecular weights within arange from 150 to 500 is 2-(vinyloxyethoxy)ethyl acrylate.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein at leastone of the polyfunctional polymerizable compounds having molecularweights within a range from 150 to 500 is a compound represented bygeneral formula (1) shown below.

CH₂═CH—CO—O—X—O—CO—CH═CH₂  (1)

(In the formula, X represents a linear or branched alkylene group of 1to 12 carbon atoms.)

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein thepolyfunctional polymerizable compounds having molecular weights within arange from 150 to 500 include 2-(vinyloxyethoxy)ethyl acrylate and acompound represented by general formula (1) shown below.

CH₂═CH—CO—O—X—O—CO—CH═CH₂  (1)

(In the formula, X represents a linear or branched alkylene group of 1to 12 carbon atoms.)

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein the amountof the compound represented by general formula (1) is from 10 to 50% bymass relative to the amount of the 2-(vinyloxyethoxy)ethyl acrylate.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein amolecular weight of the polymerization initiator is within a range from400 to 600.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein thepolymerization initiator containsoligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) andbis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

Further, another embodiment of the present invention relates to theactive energy ray-curable inkjet ink described above, wherein an amountof the bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide is from 50 to80% by mass relative to an amount of theoligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone).

Furthermore, another embodiment of the present invention relates to aninkjet recorded article obtained by printing the active energyray-curable inkjet ink described above onto a recording medium and thencuring the ink with an active energy ray.

Further, another embodiment of the present invention relates to a methodfor producing an inkjet recorded article, the method including:

a jetting step of jetting the active energy ray-curable inkjet inkdescribed above so as to impact a recording medium, and

a curing step of irradiating an active energy ray onto the active energyray-curable inkjet ink that has impacted the recording medium, therebycuring the active energy ray-curable inkjet ink.

Further, another embodiment of the present invention relates to themethod for producing an inkjet recorded article described above, whereinthe curing step is conducted under an atmosphere having an oxygenconcentration of not more than 1% by volume.

Effects of the Invention

Embodiments of the present invention are able to provide an activeenergy ray-curable inkjet ink that is resistant to migration, exhibitsexcellent jetting properties at high speed, and has a cured coating film(with good flexibility and low shrinkage) that is suitable for foodpackaging, as well as providing an inkjet recorded article that usesthis active energy ray-curable inkjet ink, and a method for producing aninkjet recorded article.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are described below in furtherdetail. However, the present invention is not limited to the embodimentsdescribed below, and also includes all manner of modifications that canbe made within the scope of the invention. Furthermore, unlessspecifically stated otherwise, “parts” represents “parts by mass” and“%” represents “% by mass”.

<Active Energy Ray-Curable Inkjet Ink>

An active energy ray-curable inkjet ink according to an embodiment ofthe present invention contains polymerizable compounds and apolymerization initiator, wherein the polymerizable compounds include atleast 5 types of polyfunctional polymerizable compounds having molecularweights within a range from 150 to 500, and include substantially nomonofunctional polymerizable compounds.

An active energy ray-curable inkjet ink of an embodiment of the presentinvention (hereafter also referred to as simply “the ink”) means an inkthat can be cured by active energy rays, wherein the term “active energyrays” means rays that can activate the polymerization initiator in theink and cause curing of the ink. Examples of the active energy raysinclude electron beams, α-rays, γ-rays, X-rays, and ultraviolet rays andthe like. The active energy rays used for curing the ink of anembodiment of the present invention are preferably an electron beam orultraviolet rays, which present little danger to humans and are easy tohandle, and ultraviolet rays are even more preferred.

Conventional active energy ray inkjet inks suffer from migration ofunreacted polymerizable compounds and the polymerization initiator fromthe coating film, and although investigations have been conducted intoreducing the amount of migration by using high-molecular weightinitiators and polymerizable compounds, the results are not totallysatisfactory, and the use of high-molecular weight compounds also makesinkjet printing at high speed impossible.

Moreover, the use of polyfunctional polymerizable compounds has alsobeen investigated, but the coating film tends to shrink during curing,and use of such compounds on food packaging which often usescomparatively thin plastic films (film thickness: 10 to 25 μm) isproblematic.

According to an embodiment of the present invention, by employing thecomposition described above, an energy ray-curable inkjet ink can beprovided that exhibits excellent jetting properties at high speed, isresistant to migration, and has a cured coating film (with goodflexibility and low shrinkage) that is suitable for food packaging.

Although the detailed mechanism is unclear, it is surmised that byincluding at least 5 types of polyfunctional polymerizable compoundshaving molecular weights within a range from 150 to 500 as polymerizablecompounds, a multitude of regions having different structures existrandomly throughout the coating film following reaction, therebyefficiently impeding the movement of unreacted polymerization initiatoror polymerizable compounds, and reducing the amount of migration withoutrequiring the use of high-molecular weight polymerization initiators andpolymerizable compounds.

The active energy ray-curable inkjet ink of an embodiment of the presentinvention is described below in further detail.

[Polymerizable Compounds]

In the description and the like of the present invention, unlessspecifically stated otherwise, the terms “(meth)acryloyl”,“(meth)acrylic acid”, “(meth)acrylate” and “(meth)acryloyloxy” mean“acryloyl and/or methacryloyl”, “acrylic acid and/or methacrylic acid”,“acrylate and/or methacrylate” and “acryloyloxy and/or methacryloyloxy”respectively. Further, “PO” means “propylene oxide” and “EO” means“ethylene oxide”.

The active energy ray-curable inkjet ink of an embodiment of the presentinvention contains polymerizable compounds. In this description, theterm “polymerizable compounds” describes compounds that undergopolymerization or crosslinking upon irradiation with active energy rays,and means compounds having at least one ethylenic unsaturated bondwithin the molecule.

Specifically, compounds having at least one group selected from among a(meth)acryloyl group, allyl group, vinyl group, vinyl ether group andinner double bond group (such as maleic acid) are preferred.

In an embodiment of the present invention, the amount of thepolymerizable compounds, relative to the total mass of the ink, ispreferably within a range from 60 to 95% by mass, and more preferablyfrom 65 to 90% by mass.

The active energy ray-curable inkjet ink of an embodiment of the presentinvention contains substantially no monofunctional polymerizablecompounds, and contains at least 5 types of polyfunctional polymerizablecompounds having molecular weights within a range from 150 to 500 as thepolymerizable compounds.

In an embodiment of the present invention, from the viewpoint of thejetting properties at high speed, the polyfunctional polymerizablecompounds having molecular weights within a range from 150 to 500 morepreferably have molecular weights of 150 to 400. Provided the molecularweights fall within this range, superior high-speed jetting propertiescan be obtained.

In an embodiment of the present invention, the expression “at least 5types of polyfunctional polymerizable compounds having molecular weightswithin a range from 150 to 500” means that the ink contains 5 or morepolyfunctional polymerizable compounds which each have a molecularweight of 150 to 500, and which each have mutually different chemicalstructures. However. EO adducts and PO adducts are counted as a singletype, even when composed of a mixture containing compounds of differentdegrees of polymerization. From the viewpoint of migration, it is morepreferable that a combination of at least 5 types but not more than 10types of polyfunctional polymerizable compounds of different chemicalstructure are used, and a combination of at least 5 types but not morethan 8 types is even more preferred. Provided the number of types ofpolyfunctional polymerizable compounds having molecular weights within arange from 150 to 500 falls within the above range, the amount ofmigration can be effectively suppressed.

In the description and the like of the present invention, the expression“contains substantially no” means that none of the indicated substanceis added intentionally. For example, monofunctional polymerizablecompounds produced as a result of transformation of a portion of thepolyfunctional polymerizable compounds during ink storage, andmonofunctional polymerizable compounds that exist as impurities withinthe polyfunctional polymerizable compounds in an embodiment of thepresent invention are not added intentionally, and therefore the ink maybe deemed to contain substantially no monofunctional polymerizablecompounds. On the other hand, in those cases where a polyfunctionalpolymerizable compound containing an intentionally added monofunctionalpolymerizable compound is used as an ink material, the ink cannot bedeemed to contain substantially no monofunctional polymerizablecompounds. Specifically, the level of impurities is preferablycontrolled so that the amount of monofunctional polymerizable compoundsin the ink is not more than 0.5% by mass. Examples of monofunctionalpolymerizable compounds include polymerizable compounds having only onegroup selected from the group consisting of a (meth)acryloyl group,allyl group, vinyl group and vinyl ether group as an ethylenicunsaturated double bond.

In an embodiment of the present invention, the polyfunctionalpolymerizable compounds are preferably compounds having two or moregroups selected from the group consisting of a (meth)acryloyl group,allyl group, vinyl group and vinyl ether group as ethylenic unsaturateddouble bonds. From the viewpoint of migration, including polyfunctionalpolymerizable compounds having two or more groups selected from thegroup consisting of a (meth)acryloyl group and a vinyl ether group ispreferred, and including polyfunctional polymerizable compounds havingone or more of each of a (meth)acryloyl group and a vinyl ether group ismore preferred. Moreover, using a combination of a polyfunctionalpolymerizable compound having two or more (meth)acryloyl groups and apolyfunctional polymerizable compound having one or more of each of anacryloyl group and a vinyl ether group is particularly preferred.

In an embodiment of the present invention, from the viewpoint of thejetting properties and migration, the total amount of polyfunctionalpolymerizable compounds having a molecular weight within a range from150 to 500, relative to the total mass of all polymerizable compounds,is preferably at least 90% by mass, and more preferably 95% by mass orgreater.

In an embodiment of the present invention, from the viewpoints ofmigration, shrinkage and flexibility, each of the compounds included inthe polyfunctional polymerizable compounds having molecular weights of150 to 500 is preferably a difunctional to tetrafunctional polymerizablecompound, is more preferably a difunctional or trifunctionalpolymerizable compound, and is particularly preferably a difunctionalpolymerizable compound.

In an embodiment of the present invention, in those cases where thepolyfunctional polymerizable compound having a molecular weight of 150to 500 is a difunctional polymerizable compound, from the viewpoint ofmigration, the amount of each compound relative to the total mass of theink is, independently, preferably within a range from 5 to 50% by mass,more preferably from 5 to 45% by mass, and particularly preferably from5 to 40% by mass. Provided the amount of each compound falls within thisrange, migration can be effectively suppressed.

In those cases where the polyfunctional polymerizable compound having amolecular weight of 150 to 500 is a trifunctional or higherpolymerizable compound, from the viewpoints of migration, shrinkageproperties and flexibility, the amount of each compound relative to thetotal mass of the ink is, independently, preferably not more than 10% bymass, more preferably not more than 5% by mass, and particularlypreferably 0.5% by mass or less.

In an embodiment of the present invention, from the viewpoint of thejetting properties, the viscosity at 25° C. of each polyfunctionalpolymerizable compound having a molecular weight of 150 to 500 ispreferably within a range from 3 to 60 mPa·s, and more preferably from 3to 20 mPa·s.

Specific examples of the polyfunctional polymerizable compound havingone or more of each of a (meth)acryloyl group and a vinyl ether groupinclude polyfunctional polymerizable compounds such as 2-vinyloxyethyl(meth)acrylate, 3-vinyloxypropyl (meth)acrylate,1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl(meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate,2-(1-vinyloxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxy)ethyl(meth)acrylate and 2-(vinyloxyethoxy)propyl (meth)acrylate.

Specific examples of the polyfunctional polymerizable compound havingtwo or more (meth)acryloyl groups include difunctional polymerizablecompounds such as 1,3-butylene glycol di(meth)acrylate, 1,4-butanedioldi(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, polyethylene glycol (200)di(meth)acrylate, polyethylene glycol (300) di(meth)acrylate,polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600)di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate,dipropylene glycol di(meth)acrylate, tripropylene glycoldi(meth)acrylate, EO (2)-modified 1,6-hexanediol di(meth)acrylate, PO(2)-modified neopentyl glycol di(meth)acrylate, (neopentylglycol-modified) trimethylolpropane di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, EO-adducted di(meth)acrylate ofbisphenol A, EO-adducted di(meth)acrylate of bisphenol F. PO-adducteddi(meth)acrylate of bisphenol A, cyclohexanedimethanol di(meth)acrylate,dimethylol-tricyclodecane di(meth)acrylate and dicyclopentanyldi(meth)acrylate:

trifunctional polymerizable compounds such as trimethylolpropanetri(meth)acrylate. ε-caprolactone-modified tris-(2-acryloyloxyethyl)isocyanurate, ethoxylated isocyanuric acid tri(meth)acrylate,tris(2-hydroxyethyl) isocyanurate tri(meth)acrylate, pentaerythritoltri(meth)acrylate and trimethylolpropane tri(meth)acrylate;

tetrafunctional polymerizable compounds such as pentaerythritoltetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate;

a pentafunctional polymerizable compound of dipentaerythritolpenta(meth)acrylate; and

a hexafunctional polymerizable compound of dipentaerythritolhexa(meth)acrylate.

In an embodiment of the present invention, the polyfunctionalpolymerizable compounds having molecular weights within a range from 150to 500 preferably include 2-(vinyloxyethoxy)ethyl acrylate as adifunctional polymerizable compound. By including2-(vinyloxyethoxy)ethyl acrylate, the curability improves, migration issuppressed, and the jetting properties at high speed become morefavorable.

In an embodiment of the present invention, from the viewpoint ofmigration and the jetting properties, the amount of2-(vinyloxyethoxy)ethyl acrylate, relative to the total mass of the ink,is preferably within a range from 20 to 50% by mass, and more preferablyfrom 30 to 45% by mass.

In an embodiment of the present invention, from the viewpoint of theinkjet jetting properties, the polyfunctional polymerizable compoundshaving molecular weights of 150 to 500 preferably include a difunctionalpolymerizable compound represented by general formula (1) shown below.

CH₂CH—CO—O—X—O—CO—CH═CH₂  (1)

(In the formula, X represents a linear or branched alkylene group of 1to 12 carbon atoms.)

In an embodiment of the present invention, from the viewpoint of thejetting properties and migration, the amount of the difunctionalpolymerizable compound represented by general formula (1) shown above,relative to the amount of 2-(vinyloxyethoxy)ethyl acrylate, ispreferably within a range from 10 to 50% by mass, and more preferablyfrom 10 to 35% by mass.

Specific examples of the difunctional polymerizable compound representedby general formula (1) shown above include 1,4-butanedioldi(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate,1,10-decanediol di(meth)acrylate and 1,2-dodecanediol di(meth)acrylate.Among these compounds, from the viewpoint of the jetting properties,difunctional polymerizable compounds in which X is a linear alkylenegroup of 6 to 10 carbon atoms are preferred, difunctional polymerizablecompounds in which X is a linear alkylene group of 6 to 9 carbon atomsare more preferred, and 1,6-hexanediol di(meth)acrylate is particularlydesirable.

In an embodiment of the present invention, from the viewpoint of theflexibility of the coating film, the polyfunctional polymerizablecompounds having molecular weights within a range from 150 to 500preferably include a difunctional polymerizable compound having ahomopolymer glass transition temperature (Tg) of −30 to +40° C. in anamount of 5 to 30% by mass relative to the total mass of the ink, andmore preferably include a difunctional polymerizable compound having ahomopolymer glass transition temperature (Tg) of −15 to +40° C. in anamount of 5 to 30% by mass relative to the total mass of the ink.Specific examples of this type of difunctional polymerizable compoundinclude EO (2)-modified 1,6-hexanediol di(meth)acrylate (Tg: −8° C.),polyethylene glycol (300) di(meth)acrylate (Tg: −13° C.), polyethyleneglycol (200) di(meth)acrylate (Tg: 13° C.), and PO (2)-modifiedneopentyl glycol di(meth)acrylate (Tg: 32° C.).

In the description and the like of the present invention, thehomopolymer glass transition temperature employs the catalog value whenavailable, or may employ a value measured by differential scanningcalorimetry (DSC) when no catalog value is available. A SeikoInstruments DSC120U is used as the DSC apparatus, with measurementconducted at a measurement temperature of 30 to 300° C. and a rate oftemperature increase of 2.5° C. per minute.

In an embodiment of the present invention, provided the ink includes atleast 5 types of polyfunctional polymerizable compounds having molecularweights within a range from 150 to 500, then the ink may, for example,also include a polyfunctional polymerizable compound having a molecularweight exceeding 500 as another polyfunctional polymerizable compound,provided the effects of the embodiment are not impaired. In this case,from the viewpoint of the jetting properties, the amount of this othercompound, relative to the total mass of the ink, is preferably less than5% by mass, more preferably not more than 3% by mass, and particularlypreferably 0.5% by mass or less.

[Polymerization Initiator]

The active energy ray-curable inkjet ink according to an embodiment ofthe present invention contains a polymerization initiator. There are noparticular limitations on the types of polymerization initiator that canbe used in embodiments of the present invention, and conventionalpolymerization initiators may be used. Further, a single polymerizationinitiator may be used alone, or a combination of two or morepolymerization initiators may be used. Polymerization initiators includenot only compounds that absorb external energy such as active energyrays to produce a polymerization-initiating species, but also compoundsthat absorb specific active energy rays to promote the decomposition ofa polymerization initiator (so-called sensitizers).

In an embodiment of the present invention, from the viewpoint ofmigration, the amount of the polymerization initiator, relative to thetotal mass of polymerizable compounds, is preferably within a range from5 to 20% by mass, and more preferably from 5 to 15% by mass.

In an embodiment of the present invention, from the viewpoints ofmigration and the jetting properties, the polymerization initiatorpreferably has a molecular weight within a range from 400 to 600, andmore preferably from 400 to 500.

Specific examples of the polymerization initiator includediphenylacylphenylphosphine oxide, ethoxy (2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide,bis (2,4,6-trimethylbenzol)-phenylphosphine oxide, thioxanthone,2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone,2,4-dimethylthioxanthone, 2,4-diethylthioxanthone,2-methyl-1-[4-(methoxythio)-phenyl]-2-morpholinopropane-1-one,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-(dimethylamino)-2-[(4-methylphenyl) methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, benzophenone, 4-phenylbenzophenone,isophthalphenome, 4-benzoyl-4′-methyl-diphenyl sulfide,1-hydroxycyclohexyl phenyl ketone,2-hydroxy-2-methyl-1-phenylpropane-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl) phenyl) propanone), bis-N,N-[4-dimethylaminobenzoyloxyethylene-1-yl]-methylamine, and1-[(4-methyl-phenyl)-sulfonyl]-propane-1-one.

Among these compounds, from the viewpoint of migration, using acombination of oligo (2-hydroxy-2-methyl-1-(4-(1-methylvinyl) phenyl)propanone) and bis (2,4,6-trimethylbenzoyl)-phenylphosphine oxide ispreferred.

From the viewpoints of migration and the jetting properties, the amountof bis (2,4,6-trimethylbenzoyl)-phenylphosphine oxide, relative to theamount of oligo (2-hydroxy-2-methyl-1-(4-(1-methylvinyl) phenyl)propanone) is preferably within a range from 50 to 80% by mass, and morepreferably from 55 to 75% by mass.

[Colorant]

The active energy ray-curable inkjet ink according to an embodiment ofthe present invention preferably contains a colorant. There are noparticular limitations on the types of colorant that can be used inembodiments of the present invention, and conventional colorants may beused, although pigments having superior weather resistance, oilresistance and water resistance are preferred. Both inorganic pigmentsand organic pigments may be used as the pigment. The types of pigmentstypically used in printing applications and coating materialapplications may be used, and a suitable pigment may be selected fromamong such pigments in accordance with the properties required such ascolor development and light resistance.

Examples of the inorganic pigment include carbon blacks such as furnaceblack, lamp black, acetylene black, and channel black, iron oxide, andtitanium oxide.

Examples of the organic pigment include soluble azo pigments such asβ-naphthol-based, β-oxynaphthoic acid-based,-oxynaphthoic acid-basedanilide-based, acetoacetate anilide-based and pyrazolone-based;insoluble azo pigments such as β-naphthol-based, β-oxynaphthoicacid-based anilide-based, acetoacetate anilide-based monoazo,acetoacetate anilide-based disazo and pyrazolone-based;phthalocyanine-based pigments such as copper phthalocyanine blue,halogenated (for example, chlorinated or brominated) copperphthalocyanine blue, sulfonated copper phthalocyanine blue andmetal-free phthalocyanine; and polycyclic pigments and heterocyclicpigments such as quinacridone-based, dioxazine-based, slene-based(pyrantron, anthanthrone, indanthrone, anthrapyrimidine, flavanthrone,thioindigo-based, anthraquinone-based, perinone-based, perylene-based,and the like), isoindolinone-based, metal complex-based,quinophtharone-based and diketopyrrolopyrrole-based.

More specifically, expressed in terms of Color Index number, thepigments exhibiting cyan color include C.I. Pigment Blue 1, 2, 14, 15,15:1, 15:2, 15:3, 15:4, 60, 62 and the like.

The pigments exhibiting magenta color include C.I. Pigment RED 1, 3, 5,19, 21, 22, 31, 38, 42, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 50, 52,53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 83, 90, 104,108, 112, 114, 122, 144, 146, 148, 149, 150, 166, 168, 169, 170, 172,173, 176, 177, 178, 184, 185, 187, 193, 202, 209, 214, 242, 254, 255,264, 266, and 269, C.I. Pigment Violet 19 and the like.

The pigments exhibiting yellow color include C.I. Pigment Yellow 1, 2,3, 12, 13, 14, 16, 17, 18, 24, 73, 74, 75, 83, 93, 95, 97, 98, 100, 108,109, 110, 114, 120, 128, 129, 138, 139, 174, 150, 151, 154, 155, 167,180, 185, 213 and the like.

The pigments exhibiting black color include C.I. Pigment Black 1, 6, 7,9, 10, 11, 28, 26, 31 and the like.

The pigments exhibiting white color include C.I. Pigment White 5, 6, 7,12, 28 and the like.

The pigments exhibiting green color include C.I. Pigment Green 1, 2, 3,4, 7, 8, 10, 15, 17, 26, 36, 45, 50 and the like.

The pigments exhibiting violet color include C.I. Pigment Violet 1, 2,3, 4, 5:1, 12, 13, 15, 16, 17, 19, 23, 25, 29, 31, 32, 36, 37, 39, 42and the like.

The pigments exhibiting orange color include C.I. Pigment Orange 13, 16,20, 34, 36, 38, 39, 43, 51, 61, 63, 64, 74 and the like.

Among the above pigments. C.I. Pigment Blue 15:3 and 15:4 are morepreferred as the pigment exhibiting cyan color. C.I. Pigment RED 122 and202, and C.I. Pigment Violet 19 are more preferred as the pigmentexhibiting magenta color, C.I. Pigment Yellow 74, 120, 139, 150, 180,185 and 213 are more preferred as the pigment exhibiting yellow color,and C.I. Pigment Black 7 is more preferred as the pigment exhibitingblack color.

In an embodiment of the present invention, a single pigment may be usedalone, or a combination of two or more pigments may be used.

In an embodiment of the present invention, the amount of the colorant,relative to the total mass of the ink, is preferably within a range from0.5 to 20% by mass, more preferably from 1 to 10% by mass, and even morepreferably from 2 to 5% by mass. By ensuring that the amount of thecolorant falls within this range, favorable results can be more easilyobtained for the color density and light resistance of printed articles.

[Pigment Dispersant]

In an embodiment of the present invention, a pigment dispersant ispreferably used to improve the pigment dispersibility and the storagestability of the inkjet ink.

There are no particular limitations on the types of pigment dispersantthat can be used in embodiments of the present invention, andconventional pigment dispersants may be used. Among such pigmentdispersants, resin-based pigment dispersants having basic functionalgroups are preferred, wherein examples of the basic functional groupsinclude primary, secondary and tertiary amino groups, andnitrogen-containing heterocycles such as pyridine, pyrimidine andpyrazine.

Further, in terms of the backbone that constitutes the resin pigmentdispersant, aliphatic amine backbones and/or urethane backbones areparticularly preferred, as they enable a pigment dispersant of favorablestorage stability to be obtained more easily.

The pigment dispersant preferably has a weight average molecular weightof 5,000 to 50,000, an acid value (mgKOH/g) of 5 to 20, and an aminevalue (mgKOH/g) of 20 to 50.

The “acid value” represents the acid value per 1 g of the pigmentdispersant solid fraction, and can be determined by a potentiometrictitration method in accordance with JIS K 0070.

The “amine value” represents the amine value per 1 g of the pigmentdispersant solid fraction, and represents a value determined by apotentiometric titration method using a 0.1 N aqueous solution ofhydrochloric acid in accordance with ASTM D2074, and then converted toan equivalent amount of potassium hydroxide.

Specific examples of the pigment dispersant include Solsperse (aregistered trademark) 32000, 76400, 76500, J100 and J180 manufactured byThe Lubrizol Corporation, Disperbyk (a registered trademark)-161, 162,163, 164, 165, 166, 167 and 168 manufactured by BYK-Chemie GmbH, AJISPER(a registered trademark) PB821 and PB822 manufactured by AjinomotoFine-Chemical Co., Inc., and EFKA (a registered trademark) PX4701manufactured by BASF Corporation.

The amount of the pigment dispersant may be selected as desired toensure the desired stability. For example, inkjet inks having superiorfluidity characteristics typically contain from 25 to 150 parts by massof the pigment dispersant per 100 parts by mass of the pigment. When thepigment dispersant is used in an amount within this range, thedispersion stability of the inkjet ink is more favorable, and even aftera long period of storage, quality similar to that initially obtainedtends to be achievable. Moreover, an amount of the pigment dispersantwithin a range from 40 to 100 parts by mass per 100 parts by mass of thepigment is preferred in terms of achieving both favorable dispersibilityand jetting properties for the inkjet ink.

[Other Components]

The inkjet ink of an embodiment of the present invention may, ifnecessary, also contain surface modifiers, polymerization inhibitors,antifoaming agents, and antioxidants and the like in addition to thecomponents described above.

In the description and the like of the present invention, a “surfacemodifier” means a substance that lowers the surface tension of the inkupon addition to the ink. Examples of surface modifiers includesilicone-based surface modifiers, fluorine-based surface modifiers,acrylic-based surface modifiers and acetylene glycol-based surfacemodifiers. Form the viewpoints of the surface tension reductioncapability and the compatibility with the polymerizable compounds, useof a silicone-based surface modifier is preferred.

Specific examples of silicone-based surface modifiers include modifiedproducts of dimethylsiloxane structures. Among such compounds,polyether-modified siloxane-based surface modifiers are preferred.

The polyether may be, for example, polyethylene oxide and/orpolypropylene oxide. In one embodiment of the present invention, apolyether-modified siloxane-based surfactant that can be obtainedcommercially may be used.

Representative examples of products that can be used favorably includepolyether-modified siloxanes such as BYK (a registered trademark)-378,348 and 349, and polyether-modified polydimethylsiloxanes such asBYK-UV3500 and UV3510, all manufactured by BYK-Chemie GmbH. Additionalexamples include polyether-modified siloxane copolymers such as TEGO (aregistered trademark) GLIDE 450, 440, 435, 432, 410, 406, 130, 110 and100, manufactured by Evonik Degussa GmbH. Among these, from theviewpoint of improving the print quality, polyether-modifiedsilicone-based surface modifiers such as BYK-331, 333, 378, 348 andUV3510, and TEGO GLIDE 450, 440, 432 and 410 are preferred.

The amount of the silicone-based surface modifier, relative to the totalmass of the inkjet ink, is preferably within a range from 0.05 to 5% bymass. By ensuring that the amount is at least 0.05% by mass, thewettability of the recording medium by the inkjet ink can be improved.On the other hand, by ensuring the amount is not more than 5% by mass,favorable storage stability can be more easily ensured for the inkjetink.

A polymerization inhibitor can be used for enhancing the viscositystability of the inkjet ink over time, the jetting stability followingstanding, and the viscosity stability inside the inkjet recordingdevice. Examples of compounds that may be used as the polymerizationinhibitor include hindered phenol-based compounds, phenothiazine-basedcompounds, hindered amine-based compounds, and phosphorus-basedcompounds.

Specific examples include 4-methoxyphenol, hydroquinone,methylhydroquinone, t-butylhydroquinone, 2,6-di-t-butyl-4-methylphenol,phenothiazine, and the aluminum salt of N-nitrosophenylhydroxylamine.Among these compounds, from the viewpoint of migration,2,6-di-t-butyl-4-methylphenol is preferred.

From the viewpoints of migration and storage stability, the amount ofthe polymerization inhibitor, relative to the total mass of the ink, ispreferably within a range from 0.01 to 1% by mass, more preferably from0.02 to 0.5% by mass, and particularly preferably from 0.05 to 0.1% bymass.

<Ink Properties> [Viscosity]

From the viewpoint of the high-speed jetting properties, the viscosityat 25° C. of the ink of an embodiment of the present invention ispreferably not more than 20 mPa·s, more preferably from 5 to 20 mPa·s,and even more preferably from 7 to 15 mPa·s.

Further, the viscosity at the jetting temperature (preferably atemperature of 25 to 50° C., and more preferably 25 to 45° C.) ispreferably within a range from 3 to 15 mPa·s, and more preferably from 5to 10 mPa·s.

[Surface Tension]

In those cases where the ink according to an embodiment of the presentinvention is recorded onto a recording medium of high hydrophobicityused in food packaging, such as a polyolefin, PET, coated paper oruncoated paper, from the viewpoint of the image formation properties,the surface tension of the ink at 25° C. is preferably within a rangefrom 20 to 40 mN/m, and more preferably from 20 to 25 mN/m.

<Inkjet Recording Method>

The ink of an embodiment of the present invention is used for inkjetrecording.

A recording method for producing an inkjet recorded article according toan embodiment of the present invention includes a jetting step ofjetting the ink of an embodiment of the present invention so as toimpact a recording medium, and a curing step of irradiating an activeenergy ray onto the active energy ray-curable inkjet ink that hasimpacted the recording medium, thereby curing the active energyray-curable inkjet ink.

Further, the curing step is preferably conducted under an atmospherehaving an oxygen concentration of not more than 1% by volume.

An inkjet recording method of an embodiment of the present invention isconducted by a single pass method in which printing is performed in asingle pass onto a transported recording medium while the inkjet head isheld in a fixed position.

[Recording Medium]

In the inkjet recording method according to an embodiment of the presentinvention, specific examples of the recording medium include plasticsubstrates formed from materials such as polypropylene (PP),polyethylene (PE), polyethylene terephthalate (PET), nylon, polystyreneand acrylics (such as PMMA) paper substrates such as art coated papers,semigloss coated papers and cast coated papers: and metal substratessuch as aluminum coated paper.

The recording medium may have a surface that is smooth or of unevenshape, and may be transparent, semi-transparent or opaque. Further, therecording medium may be composed of two or more of the varioussubstrates described above bonded together. Moreover, the recordingmedium may have a functional layer such as a releasable adhesive layeron the opposite side from the printing surface. In another embodiment ofthe recording medium, a functional layer such as an adhesive layer maybe provided on the printed surface following printing.

The thickness of recording media used in food packaging is preferablywithin a range from 2 to 100 μm, and more preferably from 6 to 50 μm.

The surfaces of plastic substrates and coated papers are preferablysubjected to a surface treatment such as a corona discharge treatment oran easy adhesion treatment. For example, conducting a corona dischargetreatment causes breakage of molecular bonds at the substrate surfaceand reaction with atmospheric oxygen radicals and ozone produced by thecorona discharge, thereby introducing polar functional groups such ashydroxyl groups, carbonyl groups and carboxyl groups. These polar groupsimprove the wetting properties and adhesion of the ink.

There are no particular limitations on the recording device used in theinkjet recording method according to an embodiment of the presentinvention, and conventional single pass inkjet recording devices fittedwith an inkjet head capable of achieving the desired resolution can beused. In other words, conventional inkjet recording devices includingcommercially available devices can be used for jetting the inkjet ink ofan embodiment of the present invention onto the recording medium.

[Jetting Step]

From the viewpoint of being able to obtain satisfactory image quality atprinting speeds associated with high-productivity single pass systems(30 to 50 m/min) the inkjet head preferably has a resolution (nozzledensity) of at least 180,000 dots/inch (300×600 dpi), and morepreferably at least 360,000 dots/inch (600×600 dpi). Further, the drivefrequency is preferably at least 20 kHz.

[Curing Step]

There are no particular limitations on the light source used in thecuring step, and conventional light sources may be used.

Specific examples include mercury lamps, xenon lamps, metal halidelamps, LEDs (light emitting diodes) such as UV-LED and ultraviolet laserdiodes (UV-LD), and gas-solid lasers. From the viewpoint of curability,the peak wavelength of the active energy rays is preferably within arange from 300 to 450 nm, and more preferably from 320 to 400 nm.

The inkjet ink of an embodiment of the present invention has favorablesensitivity, and can therefore be cured satisfactorily even withlow-output active energy rays. Specifically, satisfactory curing can beachieved with a maximum illuminance at the surface of the recordingmedium within a range from 10 to 2,000 mW/cm².

Provided the maximum illuminance at the surface of the recording mediumis at least 10 mW/cm², the curability is excellent, and tackiness of theimage or a deterioration in image quality do not occur.

Further, provided the maximum illuminance at the surface of therecording medium is not more than 2,000 mW/cm², curing of the jetted inkcomposition does not proceed excessively quickly, and imagedeterioration caused by the formation of unevenness in the image surfacecan be suppressed.

From the viewpoints of image quality and productivity, the maximumilluminance at the surface of the recording medium is preferably withina range from 100 to 1,800 mW/cm², and even more preferably from 200 to1,500 mW/cm².

The inkjet ink of an embodiment of the present invention is typicallyirradiated with the type of active energy rays described above for aperiod that is preferably within a range from 0.01 to 2 seconds, morepreferably from 0.1 to 1.5 seconds, and even more preferably from 0.3 to1 second.

Specifically, the method used for irradiating the active energy raysinvolves providing the light source at a position downstream in therecording medium transport direction from the fixed inkjet head, andconducting the irradiation using a single pass method.

In the curing step, the energy applied by the light source, namely theamount of energy (cumulative radiation) applied to the inkjet ink on therecording medium by irradiation with the active energy rays, ispreferably within a range from 100 to 1,000 mJ/cm², more preferably from150 to 800 mJ/cm², and even more preferably from 200 to 700 mJ/cm².Provided the energy falls within this range, a favorable combination ofgood productivity and suppression of migration can be achieved.

In an embodiment of the present invention, when irradiating the activeenergy rays, the atmosphere in the vicinity of the ink jetted onto therecording medium preferably has an oxygen concentration of not more than1% by volume. By using a combination of the ink of an embodiment of thepresent invention and curing in an atmosphere with an oxygenconcentration of not more than 1% by volume, migration can be furthersuppressed.

In embodiments of the present invention, examples of methods that may beused for lowering the oxygen concentration include a method in which theportion in which the active energy rays are irradiated is constructed asa closed system, and this closed system is then filled with nitrogen,carbon dioxide, or argon or the like. Examples of methods for supplyingnitrogen include methods that use a nitrogen cylinder, and methods thatuse a device for separating nitrogen and oxygen from air using hollowfibers.

The present invention is related to the subject matter disclosed inprior Japanese Application 2018-221888 filed on Nov. 28, 2018, theentire contents of which are incorporated by reference herein.

EXAMPLES

The embodiments of the present invention are described below in furtherdetail using a series of examples and comparative examples, but aspectsof the present invention are not limited to these examples. In thefollowing tables, “parts” mean “parts by weight” and “%” means “% byweight”.

Examples 1 to 36, Comparative Examples 1 to 13 (Production of PigmentDispersion)

Twenty parts of a cyan pigment PB15:4 (LIONOL (a registered trademark)BLUE FG-7400G manufactured by Toyo Color Co., Ltd.) as a pigment, 10parts of a pigment dispersant (a basic dispersant Solsperse (aregistered trademark) 32000 manufactured by The Lubrizol Corporation)and 70 parts of a polymerizable compound (dipropylene glycol diacrylate:Laromer (a registered trademark) DPGDA manufactured by BASF Corporation)were mixed together, and the mixture was then dispersed for one hour inan Eiger mill to complete production of a pigment dispersion. Thedispersion was conducted using Zr beads with a diameter of 1 mm at avolumetric fill rate of 75%.

(Production of Inks)

The mixed liquids of polymerizable compounds and polymerizationinitiators shown in Table 1 were added together gradually and stirred, asurface modifier and polymerization inhibitor were then added in theamounts shown in Table 1, and the resulting mixture was then shaken for6 hours using a shaker to produce an ink. The thus obtained ink wasfiltered through a PTFE filter having a pore size of 0.5 microns toremove coarse particles, thus preparing an evaluation ink.

TABLE 1 molecular Exam- Exam- Exam- Exam- Exam- Exam- weight ple 1 ple 2ple 3 ple 4 ple 5 ple 6 pigment PB15:4 3.00 3.00 3.00 3.00 3.00 3.00pigment dispersant SP32000 1.50 1.50 1.50 1.50 1.50 1.50 polymerizablemonofunctional LA 240 compound difunctional VEEA-Al 188.2 30.00 30.0030.00 30.00 65.00 39.00 DPGDA 242 25.00 20.00 10.00 5.00 5.00 25.00TPGDA 300 5.00 5.00 5.00 tricylodecane dimethanol 304 diacrylatePO-modified 328 15.00 15.00 15.00 10.00 5.00 15.00 (2) neopentyl glycoldiacrylate EO-modified 314 5.00 5.00 (2) 1,6-hexanediol diacrylatePEG200DA 308 10.00 10.00 10.00 10.00 5.00 1.00 PEG300DA 408 5.00compound 1,6-HDDA 226 5.00 5.00 5.00 5.00 5.00 5.00 represented3-methyl-1,5-pentanediol 226 by general diacrylate formula (1) 1,9-NDDA268 5.00 5.00 1,10-DDDA 282 5.00 trifunctional trimethylolpropanetriacrylate 296 EO-modified 560 (6) trimethylolpropane triacrylatetetrafunctional pentaerythritol tetraacrylate 352 EO-modified 528 (4)pentaerythritol tetraacrylate pentafunctional dipentaerythritolpentaacrylate 525 photopolymerization Omnirad 819 418.5 4.00 4.00 4.004.00 4.00 4.00 initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 6.00Omnirad 127 340 Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899Genorad BP-1 980 polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.200.20 0.20 surface adjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.300.30 total 100.00 100.00 100.00 100.00 100.00 100.00 evaluation resultoverall amount of migration (OML) A A A A B C amounts of migration (SML)A A A A C A jetting A A A B B A shrinkage properties A A A A A Aflexibility A A A A A A molecular Exam- Exam- Exam- Exam- Exam- Exam-weight ple 7 ple 8 ple 9 ple 10 ple 11 ple 12 pigment PB15:4 3.00 3.003.00 3.00 3.00 3.00 pigment dispersant SP32000 1.50 1.50 1.50 1.50 1.501.50 polymerizable monofunctional LA 240 compound difunctional VEEA-Al188.2 30.00 30.00 30.00 30.00 30.00 30.00 DPGDA 242 25.00 25.00 30.0030.00 30.00 30.00 TPGDA 300 tricylodecane dimethanol 304 diacrylatePO-modified 328 14.00 15.00 15.00 15.00 15.00 15.00 (2) neopentyl glycoldiacrylate EO-modified 314 (2) 1,6-hexanediol diacrylate PEG200DA 30810.00 4.50 4.50 PEG300DA 408 compound 1,6-HDDA 226 5.00 5.00 5.00 5.005.00 5.00 represented 3-methyl-1,5-pentanediol 226 by general diacrylateformula (1) 1,9-NDDA 268 1.00 1,10-DDDA 282 trifunctionaltrimethylolpropane triacrylate 296 10.00 5.00 0.50 EO-modified 560 (6)trimethylolpropane triacrylate tetrafunctional pentaerythritoltetraacrylate 352 5.00 0.50 EO-modified 528 (4) pentaerythritoltetraacrylate pentafunctional dipentaerythritol pentaacrylate 525photopolymerization Omnirad 819 418.5 4.00 4.00 4.00 4.00 4.00 4.00initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 6.00 Omnirad 127 340Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899 Genorad BP-1 980polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.20 0.20 0.20 surfaceadjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.30 0.30 total 100.00100.00 100.00 100.00 100.00 100.00 evaluation result overall amount ofmigration (OML) A C B A B A amounts of migration (SML) A C B A B Ajetting A C B A B A shrinkage properties A C B A C A flexibility A C B AC A molecular Exam- Exam- Exam- Exam- Exam- Exam- weight ple 13 ple 14ple 15 ple 16 ple 17 ple 18 pigment PB15:4 3.00 3.00 3.00 3.00 3.00 3.00pigment dispersant SP32000 1.50 1.50 1.50 1.50 1.50 1.50 polymerizablemonofunctional LA 240 compound difunctional VEEA-Al 188.2 10.00 20.0040.00 50.00 60.00 DPGDA 242 30.00 30.00 30.00 20.00 15.00 5.00 TPGDA 30015.00 5.00 tricylodecane dimethanol 304 diacrylate PO-modified 328 15.0020.00 20.00 10.00 5.00 5.00 (2) neopentyl glycol diacrylate EO-modified314 (2) 1,6-hexanediol diacrylate PEG200DA 308 15.00 10.00 10.00 10.0010.00 5.00 PEG300DA 408 compound 1,6-HDDA 226 10.00 10.00 5.00 5.00 5.0010.00 represented 3-methyl-1,5-pentanediol 226 by general diacrylateformula (1) 1,9-NDDA 268 1,10-DDDA 282 trifunctional trimethylolpropanetriacrylate 296 EO-modified 560 (6) trimethylolpropane triacrylatetetrafunctional pentaerythritol tetraacrylate 352 EO-modified 528 (4)pentaerythritol tetraacrylate pentafunctional dipentaerythritolpentaacrylate 525 photopolymerizaton Omnirad 819 416.5 4.00 4.00 4.004.00 4.00 4.00 initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 6.00Omnirad 127 340 Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899Genorad BP-1 960 polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.200.20 0.20 surface adjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.300.30 total 100.00 100.00 100.00 100.00 100.00 100.00 evaluation resultoverall amount of migration (OML) C B A A A A amounts of migration (SML)C B B A A B jetting B B A A A A shrinkage properties A A A A A Aflexibility A A A A A A molecular Exam- Exam- Exam- Exam- Exam- Exam-weight ple 19 ple 20 ple 21 ple 22 ple 23 ple 24 pigment PB15:4 3.003.00 3.00 3.00 3.00 3.00 pigment dispersant SP32000 1.50 1.50 1.50 1.501.50 1.50 polymerizable monofunctional LA 240 compound difunctionalVEEA-Al 188.2 30.00 30.00 30.00 30.00 30.00 30.00 DPGDA 242 20.00 20.0025.00 25.00 25.00 25.00 TPGDA 300 tricylodecane dimethanol 304diacrylate PO-modified 328 15.00 10.00 15.00 15.00 15.00 15.00 (2)neopentyl glycol diacrylate EO-modified 314 (2) 1,6-hexanedioldiacrylate PEG200DA 308 10.00 10.00 10.00 10.00 10.00 10.00 PEG300DA 4085.00 compound 1,6-HDDA 226 10.00 20.00 represented3-methyl-1,5-pentanediol 226 5.00 by general diacrylate formula (1)1,9-NDDA 268 5.00 1,10-DDDA 282 5.00 trifunctional trimethylolpropanetriacrylate 296 EO-modified 560 (6) trimethylolpropane triacrylatetetrafunctional pentaerythritol tetraacrylate 352 EO-modified 528 (4)pentaerythritol tetraacrylate pentafunctional dipentaerythritolpentaacrylate 525 photopolymerizaton Omnirad 819 416.5 4.00 4.00 4.004.00 4.00 4.00 initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 6.00Omnirad 127 340 Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899Genorad BP-1 960 polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.200.20 0.20 surface adjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.300.30 total 100.00 105.00 100.00 100.00 100.00 100.00 evaluation resultoverall amount of migration (OML) A B B A A A amounts of migration (SML)A B B A A A jetting A A C B B C shrinkage properties A A A A A Aflexibility A A A A A A molecular Exam- Exam- Exam- Exam- Exam- Exam-weight ple 25 ple 26 ple 27 ple 28 ple 29 ple 30 pigment PB15:4 3.003.00 3.00 3.00 3.00 3.00 pigment dispersant SP32000 1.50 1.50 1.50 1.501.50 1.50 polymerizable monofunctional LA 240 compound difunctionalVEEA-Al 188.2 40.00 40.00 40.00 40.00 30.00 30.00 DPGDA 242 25.00 20.0010.00 10.00 22.00 25.00 TPGDA 300 10.00 tricylodecane dimethanol 304diacrylate PO-modified 328 15.00 15.00 15.00 (2) neopentyl glycoldiacrylate EO-modified 314 10.00 15.00 (2) 1,6-hexanediol diacrylatePEG200DA 308 15.00 10.00 10.00 PEG300DA 408 10.00 15.00 compound1,8-HDDA 226 5.00 5.00 5.00 5.00 7.50 5.00 represented3-methyl-1,5-pentanediol 226 by general diacrylate formula (1) 1,9-NDDA288 5.00 1,10-DDDA 282 trifunctional trimethylolpropane triacrylate 296EO-modified 560 0.50 (6) trimethylolpropane triacrylate tetrafunctionalpentaerythritol tetraacrylate 352 EO-modified 528 (4) pentaerythritoltetraacrylate pentafunctional dipentaerythritol pentaacrylate 525photopolymerization Omnirad 819 418.5 4.00 4.00 4.00 4.00 4.00 3.00initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 7.00 Omnirad 127 340Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899 Genorad BP-1 960polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.20 0.20 0.20 surfaceadjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.30 0.30 total 100.00100.00 100.00 100.00 100.00 100.00 evaluation result overall amount ofmigration (OML) A A A A A B amounts of migration (SML) A A A A A Bjetting A A A A B A shrinkage properties A A A A B A flexibility C A A AB A molecular Exam- Exam- Exam- Exam- Exam- Exam- weight ple 31 ple 32ple 33 ple 34 ple 35 ple 36 pigment PB15:4 3.00 3.00 3.00 3.00 3.00 3.00pigment dispersant SP32000 1.50 1.50 1.50 1.50 1.50 1.50 polymerizablemonofunctional LA 240 compound difunctional VEEA-Al 188.2 30.00 30.0030.00 30.00 30.00 30.00 DPGDA 242 25.00 25.00 25.00 25.00 25.00 25.00TPGDA 300 tricylodecane dimethanol 304 diacrylate PO-modified 328 15.0015.00 15.00 15.00 15.00 15.00 (2) neopentyl glycol diacrylateEO-modified 314 (2) 1,6-hexanediol diacrylate PEG200DA 308 10.00 10.0010.00 10.00 10.00 10.00 PEG300DA 408 compound 1,8-HDDA 226 5.00 5.005.00 5.00 5.00 5.00 represented 3-methyl-1,5-pentanediol 226 by generaldiacrylate formula (1) 1,9-NDDA 288 1,10-DDDA 282 trifunctionaltrimethylolpropane triacrylate 296 EO-modified 560 (6)trimethylolpropane triacrylate tetrafunctional pentaerythritoltetraacrylate 352 EO-modified 528 (4) pentaerythritol tetraacrylatepentafunctional dipentaerythritol pentaacrylate 525 photopolymerizationOmnirad 819 418.5 3.40 3.50 4.40 5.00 4.00 initiator EsaONE 438 6.606.50 5.60 5.00 6.00 Omnirad 127 340 Omnirad 379 380.5 4.00 Omnipol 9101024 SPEEDCURE7010 1899 Genorad BP-1 960 6.00 polymerization inhibitorIonol CP 0.20 0.20 0.20 0.20 0.20 0.20 surface adjusting agentTegoGlide432 0.30 0.30 0.30 0.30 0.30 0.30 total 100.00 100.00 100.00100.00 100.00 100.00 evaluation result overall amount of migration (OML)A A A A C A amounts of migration (SML) A A A A C A jetting A A A B A Cshrinkage properties A A A A A A flexibility A A A A A A Com- Com- Com-Com- Com- Com- par- par- par- par- par- par- molec- ative ative ativeative ative ative ular Exam- Exam- Exam- Exam- Exam- Exam- weight ple 1ple 2 ple 3 ple 4 ple 5 ple 6 pigment PB15:4 3.00 3.00 3.00 3.00 3.003.00 pigment dispersant SP32000 1.50 1.50 1.50 1.50 1.50 1.50 polymeri-monofunctional LA 240 zable difunctional VEEA-Al 186.2 30.00 30.00 30.0030.00 compound DPGDA 242 40.00 40.00 35.00 25.00 35.00 25.00 TPGDA 30020.00 tricylodecane dimethanol 304 diacrylate PO-modified 328 15.0020.00 15.00 15.00 15.00 (2) neopentyl glycol diacrylate EO-modified 314(2) 1,6-hexanediol diacrylate PEG200DA 308 15.00 15.00 15.00 PEG300DA408 compound 1,6-HDDA 226 15.00 15.00 5.00 represented3-methyl-1,5-pentanediol 226 by general diacrylate formula (1) 1,9-NDDA268 1,10-DDDA 282 trifunctional trimethylolpropane 298 triacrylateEO-modified 560 10.00 (8) trimethylolpropane triacrylate tetrafunctionalpentaerythritol tetraacrylate 352 EO-modified 528 (4) pentaerythritoltetraacrylate pentafunctional dipentaerythritol 525 pentaacrylatephotopolymerization Omnirad 819 418.5 4.00 4.00 4.00 4.00 4.00 4.00initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 6.00 Omnirad 127 340Omnirad 379 380.5 Omnipol 910 1024 SPEEDCURE7010 1899 Genorad BP-1 960polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.20 0.20 0.20 surfaceadjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.30 0.30 total 100.00100.00 100.00 100.00 100.00 100.00 evaluation overall amount migration(OML) E E E D E D result amounts of migration (SML) E C D D E C jettingB B B A B D shrinkage properties A A A A A B flexibility C B A A A BCom- Com- Com- Com- Com- Com- Com- par- par- par- par- par- par- par-molec- ative ative ative ative ative ative ative ular Exam- Exam- Exam-Exam- Exam- Exam- Exam- weight ple 7 ple 8 ple 9 ple 10 ple 11 ple 12ple 13 pigment PB15:4 3.00 3.00 3.00 3.00 3.00 3.00 3.00 pigmentdispersant SP32000 1.50 1.50 1.50 1.50 1.50 1.50 1.50 polymeri-monofunctional LA 240 5.00 5.00 5.00 zable difunctional VEEA-Al 186.230.00 30.00 30.00 30.00 30.00 72.50 compound DPGDA 242 30.00 25.00 25.0020.00 20.00 TPGDA 300 5.00 tricylodecane dimethanol 304 30.00 diacrylatePO-modified 328 19.50 15.00 15.00 15.00 15.00 5.00 (2) neopentyl glycoldiacrylate EO-modified 314 (2) 1,6-hexanediol diacrylate PEG200DA 30810.00 10.00 PEG300DA 408 compound 1,6-HDDA 226 5.00 5.00 10.00 5.00represented 3-methyl-1,5-pentanediol 226 by general diacrylate formula(1) 1,9-NDDA 268 1,16-DDDA 282 trifunctional trimethylolpropane 298triacrylate EO-modified 560 0.50 30.00 (8) trimethylolpropanetriacrylate tetrafunctional pentaerythritol 352 tetraacrylateEO-modified 528 10.00 20.00 (4) pentaerythritol tetraacrylatepentafunctional dipentaerythritol 525 20.00 pentaacrylatephotopolymerization Omnirad 819 418.5 4.00 4.00 4.00 4.00 4.00 4.00initiator EsaONE 438 6.00 6.00 6.00 6.00 6.00 Omnirad 127 340 2.50Omnirad 379 380.5 Omnipol 910 1024 5.00 SPEEDCURE7010 1899 1.00 GenoradBP-1 960 polymerization inhibitor Ionol CP 0.20 0.20 0.20 0.20 0.20 0.200.20 surface adjusting agent TegoGlide432 0.30 0.30 0.30 0.30 0.30 0.300.30 total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 evaluationoverall amount migration (OML) D D E E E D D result amounts of migration(SML) D D E E E D E jetting B E A A A D E shrinkage properties A C A A AE E flexibility A C A A A E D

Details of each material in Table 1 are shown in Table 2.

TABLE 2 pigment PB15:4 Pigment Blue 15:4 pigment dispersant SP32000Basic dispersant “Solsperse 32000” manufactured by Lubrizolepolymerizable monofunctional LA lauryl acrylate compound difunctionalVEEA-Al acrylic acid 2-(2-vinyloxyethoxy) ethyl DPGDA dipropylene glycoldiacylate TPGDA tripropylene glycol diacrylate tricylodecane dimethanoldiacrylate PO-modified (2) neopentyl glycol diacrylate EO-modified (2)1,8-hexanediol diacrylate PEG200DA polyethylene glycol (200) diacrylatePEG300DA polyethylene glycol (300) diacrylate compound 1,6-HDDA1,8-hexanediol diacrylate represented 3-methyl-1,5-pentanedioldiacrylate by general 1,9-NDDA 1,9-nonanediol diacrylate formula (1)1,10-DDDA 1,10-decanediol diacrylate trifunctional trimethylolpropanetriacrylate EO-modified (8) trimethylolpropane triacrylatetetrafunctional pentaerytritol tetraacrylate EO-modified (4)penaerythritol tetraacrylate pentafunctional dipentaerythritolpentaacrylate photopolymerization Omnirad 819 bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide initiator EsaONE oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl) propanone) Omnirad 1272-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-oneOmnirad 3792-(dimethylamino)-2-[(4-ethylphenyl)methyl]-1-[4-(4-morpholinly)phenyl]-1-butanone Omnipol 910 polyethylene glycol (200)di(β-4(4-(2-dimethylammino-2-benzyl) butaonylphenyl] piperazine)SPEEDCURE1,3-di({α-[1-chloro-9-oxo-9H-thioxenthen-4-yl]oxy}acetylpoly[oxy(1- 7010methylethylene)])oxy)-2,2-bis([α-(1-chloro-9-oxo-9H-thioxanthen-4-yl]oxy}acetylpoly[oxy(1-methylethylene)])oxymethyl)propane Genorad BP-1(carboxymethoxymethoxy-benzophenone)-(polytetramethylene glycol 250)diester polymerization Ionol CP 2,6-di-tert-butyl-4-methylphenolinhibitor surface adjusting TegoGlide432 Polyether-modified siloxanecopolymer “TegoGlide 432” agent manufactured by Evonik Degussa GmbHpigment PB15:4 “LIONOL BLUE FG-7400G” manufactured by Toyocolor Co.,Ltd. pigment dispersant SP32000 Basic dispersant “Solsperse 32000”manufactured by Lubrizole polymerizable monofunctional LA “SartomerSR355” manufactured by Arkema Inc. compound difunctional VEEA-Al“VEEA-Al” manufactured by Nippon shokubai co., Ltd. DPGDA “LaromerDPGDA” manufactured by BASF TPGDA “Sartomer SR306” manufactured byArkema Inc. tricylodecane dimethanol “Sartomer SR833” manufactured byArkema Inc. diacrylate PO-modified (2) neopentyl “Sartomer SR9003”manufactured by Arkema Inc. glycol diacrylate EO-modified (2) “MIRAMERM202” manufactured by MIWON 1,8-hexanediol diacrylate SpecialityChemical co., Ltd. PEG200DA “Sartomer SR259” manufactured by Arkema Inc.PEG300DA “MIRAMER M282” manufactured by MIWON Speciality Chemical co.,Ltd. compound 1,6-HDDA “Sartomer SR238” manufactured by Arkema Inc.represented 3-methyl-1,5-pentanediol “LIGHT ACRYLATE MPD-A” manufacturedby by general diacrylate Kyoeisha chemical co., Ltd. formula (1)1,9-NDDA “Viscoat #260” manufactured by Osaka organic chemical industryLtd. 1,10-DDDA “Sartomer CD595” manufactured by Arkema Inc.trifunctional trimethylolpropane “Sartomer SR351” manufactured by ArkemaInc. triacrylate EO-modified (8) “Sartomer SR449” manufactured by ArkemaInc. trimethylolpropane triacrylate tetrafunctional pentaerytritol“Sartomer SR295” manufactured by Arkema Inc. tetraacrylate EO-modified(4) “Sartomer SR494” manufactured by Arkema Inc. penaerythritoltetraacrylate pentafunctional dipentaerythritol “Sartomer SR399”manufactured by Arkema Inc. pentaacrylate photopolymerization Omnirad819 “Omnirad 819” manufactured by IGM Resins B.V. initiator EsaONE“Esacure One” manufactured by Lamberti Omnirad 127 “Omnirad 127”manufactured by IGM Resins B.V. Omnirad 379 “Omnirad 379” manufacturedby IGM Resins B.V. Omnipol 910 “Ominipol 910” manufactured by IGM ResinsB.V. SPEEDCURE 7010 “SPEEDCURE 7010” manufactured by Lambson Ltd.Genorad BP-1 “Genorad BP-1” manufactured by Rahn AG polymerization IonolCP “Ionol CP” manufactured by Japan Chemtech inhibitor surface adjustingTegoGlide432 Polyether-modified siloxane copolymer “TegoGlide agent 432”manufactured by Evonik Degussa GmbH

[Evaluation Items] (Migration Evaluation Method)

A migration evaluation image was printed with the prepared ink using aOnePass JET device manufactured by Tritek Co., Ltd. The prepared ink wasinjected into an inkjet head manufactured by Kyocera Corporation using asyringe, a 100% solid printed image (with a film thickness equivalent to6μ) was output at a printing speed of 50 m/minute and a head temperatureof 40° C., and the image was then cured using a UV lamp (240 W)manufactured by Nordson Advanced Technology Corporation. A semiglosspaper (60#) manufactured by Avery Products Corporation was used as theprinting substrate.

The obtained printed article was bonded uniformly to a PET substrate(Lumirror (a registered trademark) manufactured by Toray Industries,Inc.) with a thickness of 25 μm using a hand roller to prepare anevaluation sample.

Using this evaluation sample, an evaluation of the overall amount ofmigration (OML) through the PET substrate, and evaluations of thespecific amounts of migration (SML) of the polymerizable compounds, thepolymerization initiators and the polymerization inhibitor wereconducted in accordance with the conditions prescribed in EuropeanRegulation (EU) No. 10/2011, CEN Standard EN 1186-1 and CEN Standard EN13130-1.

The overall amount of migration (OML) was evaluated using the followingcriteria.

A evaluation: less than 1 ppm

B evaluation: at least 1 ppm but less than 5 ppm

C evaluation: at least 5 ppm but less than 10 ppm

D evaluation: at least 10 ppm but less than 20 ppm

E evaluation: 20 ppm or greater

Evaluations of C or better were judged to indicate a practically usablelevel.

The evaluation results are shown in Table 1.

The specific amounts of migration (SML) were evaluated by measuring theamounts of migration of the polymerizable compounds and thepolymerization initiators, and then evaluating the measured amountsagainst the following criteria.

A evaluation: the measured values for the polymerizable compounds andthe polymerization initiators are below the lower limit for detection (5ppb)

B evaluation: the measured values for the polymerizable compounds are atleast as high as the lower limit for detection (5 ppb) but less than 10ppb, and the measured values for the polymerization initiators are belowthe lower limit for detection (5 ppb)

C evaluation: the measured values for the polymerizable compounds are atleast as high as the lower limit for detection (5 ppb) but less than 10ppb, and the measured values for the polymerization initiators are allbelow the upper limit prescribed in the Swiss Ordinance.

D evaluation: the measured value for only one substance among thepolymerizable compounds and the polymerization initiators exceeds theupper limit prescribed in the Swiss Ordinance.

E evaluation: the measured values for two or more substances among thepolymerizable compounds and the polymerization initiators exceeds theupper limit prescribed in the Swiss Ordinance.

Evaluations of C or better were judged to indicate a practically usablelevel.

The evaluation results are shown in Table 1.

(Jetting Evaluation)

Each of the prepared inks was subjected to a jetting evaluation using aDot View device manufactured by Tritek Co., Ltd. The prepared ink wasinjected into an inkjet head (20 kHz) manufactured by KyoceraCorporation using a syringe, the ink was then jetted from the head at ahead temperature of 40° C. and the jetting speed and the form of theliquid droplets during ink flight were analyzed. An evaluation wasconducted using the following criteria.

A evaluation: jetting speed exceeding 8 mi/minute, no divided droplet orsatellite droplet

B evaluation: jetting speed of 7 to 8 m/minute, no divided droplet orsatellite droplet

C evaluation: jetting speed of 7 to 8 m/minute, no divided droplet butsome satellite droplet

D evaluation: jetting speed of 6 to 7 m/minute, no divided droplet butsome satellite droplet

E evaluation: jetting speed of 6 to 7 m/minute, both divided droplet andsatellite droplet

Evaluations of C or better were judged to indicate a practically usablelevel.

The evaluation results are shown in Table 1.

(Shrinkage Properties)

A sample prepared by printing the prepared ink at a coverage rate of100% onto a PET substrate (Lumirror (a registered trademark)manufactured by Toray Industries, Inc.) with a thickness of 50 μm wascut into a short strip of 1 cm×5 cm, one short side of the sample wassecured to a metal substrate with tape, and the height to which thenon-secured short side of the sample lifted off the metal plate wasdeemed the initial shrinkage. Subsequently, this sample was left tostand for one day in 45° C. environment inside an oven, the sample wasremoved from the oven, and the height to which the non-secured portionof the sample had lifted off the metal plate was deemed the shrinkageupon standing. The shrinkage was evaluated against the followingcriteria.

A evaluation: the initial shrinkage is at least 0 mm but less than 5 mm,and the shrinkage upon standing is at least 0 mm but less than 7 mm

B evaluation: the initial shrinkage is at least 0 mm but less than 5 mm,and the shrinkage upon standing is at least 7 mm but less than 10 mm

C evaluation: the initial shrinkage is at least 0 mm but less than 5 mm,and the shrinkage upon standing is at least 10 mm

D evaluation: the initial shrinkage is at least 5 mm but less than 10mm, and the shrinkage upon standing is at least 10 mm

E evaluation: the initial shrinkage and the shrinkage upon standing areboth 10 mm or greater

Evaluations of C or better were judged to indicate a practically usablelevel.

The evaluation results are shown in Table 1.

(Flexibility)

A flexibility evaluation was conducted by printing the prepared ink ontoa PET film (PET50 K2411 manufactured by Lintec Corporation) in an amountsufficient to form a coating film thickness of 8 μm, curing the printedfilm, folding the resulting film into a mountain fold with the coatingfilm facing upward, and recording the number of times this foldingoperation could be performed before cracks occurred. Evaluation wasperformed against the following criteria.

A evaluation: number of folding repetitions before cracks occurred is atleast 4, or no cracks occur

B evaluation: cracks occur on the third folding repetition

C evaluation: cracks occur on the second folding repetition

D evaluation: cracks occur on the first folding repetition

E evaluation: coating film completely destroyed on first foldingrepetition

Evaluations of C or better were judged to indicate a practically usablelevel.

The evaluation results are shown in Table 1.

Based on the above results, it was evident that the ink of an embodimentof the present invention exhibited excellent jetting properties at highspeed, is resistant to migration and has a cured coating film (with goodflexibility and low shrinkage) that is suitable for food packaging.

1. An active energy ray-curable inkjet ink containing polymerizablecompounds and a polymerization initiator, wherein the polymerizablecompounds include at least 5 types of polyfunctional polymerizablecompounds having molecular weights within a range from 150 to 500, andinclude substantially no monofunctional polymerizable compounds.
 2. Theactive energy ray-curable inkjet ink according to claim 1, wherein theat least 5 types of polyfunctional polymerizable compounds havingmolecular weights within a range from 150 to 500 are composed of atleast one type of compound selected from the group consisting ofdifunctional polymerizable compounds and trifunctional polymerizablecompounds.
 3. The active energy ray-curable inkjet ink according toclaim 1, wherein the at least 5 types of polyfunctional polymerizablecompounds having molecular weights within a range from 150 to 500 aredifunctional polymerizable compounds, and the amount of each of thedifunctional polymerizable compounds is, independently, from 5 to 50% bymass relative to the total mass of the ink.
 4. The active energyray-curable inkjet ink according to claim 1, wherein one of thepolyfunctional polymerizable compounds having molecular weights within arange from 150 to 500 is 2-(vinyloxyethoxy)ethyl acrylate.
 5. The activeenergy ray-curable inkjet ink according to claim 1, wherein at least oneof the polyfunctional polymerizable compounds having molecular weightswithin a range from 150 to 500 is a compound represented by generalformula (1) shown below.CH₂═CH—CO—O—X—O—CO—CH═CH₂  (1) (In the formula, X represents a linear orbranched alkylene group of 1 to 12 carbon atoms.)
 6. The active energyray-curable inkjet ink according to claim 1, wherein the polyfunctionalpolymerizable compounds having molecular weights within a range from 150to 500 include 2-(vinyloxyethoxy)ethyl acrylate and a compoundrepresented by general formula (1) shown below.CH₂═CH—CO—O—X—O—CO—CH═CH₂  (1) (In the formula, X represents a linear orbranched alkylene group of 1 to 12 carbon atoms.)
 7. The active energyray-curable inkjet ink according to claim 6, wherein the amount of thecompound represented by general formula (1) is from 10 to 50% by massrelative to the amount of the 2-(vinyloxyethoxy)ethyl acrylate.
 8. Theactive energy ray-curable inkjet ink according to claim 1, wherein amolecular weight of the polymerization initiator is within a range from400 to
 600. 9. The active energy ray-curable inkjet ink according toclaim 1, wherein the polymerization initiator containsoligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone) andbis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.
 10. The active energyray-curable inkjet ink according to claim 9, wherein an amount of thebis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide is from 50 to 80% bymass relative to an amount of theoligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone).
 11. Aninkjet recorded article obtained by printing the active energyray-curable inkjet ink according to claim 1 onto a recording medium andthen curing the ink with an active energy ray.
 12. A method forproducing an inkjet recorded article, the method including: a jettingstep of jetting the active energy ray-curable inkjet ink according toclaim 1 so as to impact a recording medium, and a curing step ofirradiating an active energy ray onto the active energy ray-curableinkjet ink that has impacted the recording medium, thereby curing theactive energy ray-curable inkjet ink.
 13. The method for producing aninkjet recorded article according to claim 12, wherein the curing stepis conducted under an atmosphere having an oxygen concentration of notmore than 1% by volume.